Plunger switch-key.



(J. A. SHANN.

PLUNGER SWITCH KEY.

APPLICATION FILED use. 6 191a,

Llfi fi f, Patented Dec. 14. 1915.

Fig,

.1 rnnur opinion OSCAR ALANSON SHANN, 0F BROOKLYN, NEW YORK, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, NEW YORK, N. Y., A CORPORATION OF ILLINOIS.

- rnunenn SWITCH-KEY.

Specification of Letters Patent.

rammed nee. i ism.

Application filed December '6, 1913. Serial No. 805,184.

To all whom it may concern:

Be it known that I, OSCAR ALANsoN SHANN, a citizen of the United States, residing at Brooklyn, in the county of Kings and State of New York, have invented a certain new and useful Improvement in Plunger Switch-Keys, of which the following is a full, clear, concise, and exact description.

, tion of the plunger, whereby new contact surfaces are constantly presented at the portion of the plunger which engages the contact springs. The means provided may comprise a loose connecting means for securing the plunger in the frame, which connecting means permits the free rotation of the said plunger and at the same time limits the longitudinal movement thereof. This may be accomplished by providing a retaining means for the plunger comprising a curved spring member engaging a groove in the plunger and having a projection thereon which engages an opening in the frame of the key.

Figure 1 is a side elevation, partly in section, showing this invention as applied to a plunger switch key; Fig. 2 is a sectional view of the parts shown in Fig. 1; Fig. 3 is a detail perspective view of the plunger and retaining member; Fig. dis a perspective view of the end of the frame in which the plunger is carried; Fig. 5 shows a modified form of the retaining member.

In the structure shown, the tubular shell 1 has sets of contact-springs 2, 2 mounted on one end of said shell, and the plunger 3 mounted on the opposite end, said contact springs being positioned so as to be in operative relation to said plunger. The plunger 3 has an annular groove 4 which is adapted to receive a retainer 5 as shown m Fig. 3. Saidretainer 5 has a projection 6 which engages in the aperture 7, thereby furnishing the means for fastening the plunger 3 in shell 1. The shape of the pro ection 6 may be modified as is shown in Figs. 3 and 5. in the former it is an embossing, while in the latter it is a punching. The

cap 8 on'the upper portion of the plunger engages with the edge 9 of shell 1 when said plunger is depressed, and thereby limits the downward movement of said plunger.

The aperture 7 being oblong in shape, as shown in Fig. 4, permits the projection 6 on retainer 5 tomove longitudinally in the shell 1 upon the depression or" the plunger. W'lren the plunger is in normal position the pro ect1on bears against edge 10 of the aperture 7, preventing a dislocation of said plunger and thereby limiting its longitudinal movement. Suflicient tension to keep the retainer 5 in close engagement with the aperture 7 in the shell is obtained by making the inner radius of the curved spring, which forms the body portion of said retainer,

slightly less than that of the bottom' of groove 4 in the plunger 3.

It will be seen from the above description that the means provided limits the reciprocal movement of the plunger, and at the same time allows it to rotate freely, thereby distributing the wear of the contact springs over the entire working surface of said plunger, and thus preventing grooves from being worn on said working surface, which greatly impairs the efficiency of a plungertype key.

I claim:

1. In a key structure in combination a means and plunger being relatively rotatable about a common axis.

3. In a key structure in combination a frame, an operating plunger having annular groove therein and a rotatable retaining means for said plunger and said "frame adapted to register in said groove.

4-. in a key structure in combination a frame having an aperture therein, an operating plunger having a" annular groove therein, a loose connecting means adapted to means? register in said groove, said loose connecting,

means having a projection thereon, said projeotion adapted to engage in said aperture.

5. In a key structure in combination a 5 frame having an aperture therein, an operatine; plunger having an annular groove therein, a loose connecting means adapted to register in saicl groove, said loose connecting means comprising a curved flat spring 10 booly portion having its inner radius slightly less than that of the bottom of said annular groove, and a projection thereon engaging the aperture in said frame.

In witness whereof, I hereunto subscribe my name this 3rd day of December, A. D. 15 I OSCAR ALANSON SHANN. lNitneSses: NANON E. TUTHILL, ALICE HAZLEY. 

